Electronic computer



v Oct. 14, 1947. J. A. RAJCHMAN ELECTRONIC COMPUTER 2 Sheets-Sheet 2lll! :hun

Filed Jan. 22, 1943 JIL-f.

J Ir. ai.. a m m r E f a@ sur u afm a a s? m 3. mw c we F mi l s I l l lI L nventor attorney Patented Oct. 14, 1947 ELECTRONIC COMPUTER Jan A.Rajchman, PrincetonjN. J., asslgnor to Radio Corporation of Delaware ofAmerica, a corporation Application January 22, 1943, Serial No. 473,2559 Claims. (Cl. 235-61) This invention relates generally to electroniccomputers and particularly to an improved meth- While the particulardevice to be rdisclosed hereinafter utilizes some mechanical means, itshould be understood that variations in speed and arrangement thereofwill not materially affect the accuracy of the computation performed bythe device. For purpose of illustration, apparatus is disclosed hereinwhich will provide any desired' function of a single variable which isapplied to the device in the form of voltage pulses.

A variable X may be applied to the apparatus in the form of regularlyoccurring voltage pulses. These pulses are applied through an electronicswitch of any type .well known inthe art to, and counted upon, aconventional pulse counter which may be of the type described in thecopending U. S. application of George A. Merton and Leslie E. Flory,Serial No. 464.293, led November 2, 1942. Two transparent discs, havingopaque ilducial marks, are rotated in phase by a motor. Separate lightsources, associated with each rotating disc, respectively actuate twolight-sensitive devices. One of the light sensitive devices associatedwith each disc may, for example, be actuated continuously during eachhalf revolution of the disc, while the other light sensitive device isactuated simultaneously therewith by the interruption of the light beamby the fiducia] marks on the disc. One disc should preferably haveequally spaced fiducial marks while the other disc has ducial marksspaced according to the particular function to be derived from theapparatus.

The rst light sensitive device which is actur ated continuously duringeach alternate half revolution, and inactive during the next halfrevolution, controls the operation of an electronic switch in such amanner that the X pulses arey counted upon the X counter during theinactive interval of the light sensitive device. The light sensitivedevice `then actuates the electronic switch to apply the pulses derivedfrom the light sensitive device actuated by the equi-spaced ducial marksto subtract pulses from, or uncount the counter until its count is zero.At this point, a zero control signal is derived from the X counter.

Similarly, the light sensitive device associated with the secondrotating disc which is actuated continuously during each alternate halfrevolution of the disc, controls a second electronic switch 2 which isconnected to a second counter for the desired function of X, i. e.,f(X). The pulses derived from the light sensitive device which isassociated with the ducial marks on the second rotating disc, areapplied to a third electronic switch which is opened by the zero signalfrom the X counter. When the first light sensitive device associatedwith the second disc is actuated, the pulses derived from the secondlight sensitive device associated with the same disc are applied throughthe second and third electronic switches to the f(X) counter. The zerosignal derived from the X counter when the count thereon reaches zerovalue interrupts the application of these pulses to the f (X) counter.When the second disc has completed one half revolution, the first lightsensitive device associated therewith operates the second electronicswitch to subtract pulses from, or subtract" the flX) counter andprovide a train of pulses at the outf put terminals which ischaracteristic of the desired function of X.

Among the obiects of the invention are to provide an improved method ofand means for counting voltage pulses. Another object is lto provide animproved method of and means for deriving a predetermined function of avariable in which the variable is inthe form of regularly occurringvoltage pulses which control duration of the count of irregularlyoccurring voltage pulses applied to an electronic counter.

The invention will be described by reference to the accompanying drawingof which Figure 1 is a schematic block circuit diagram of one embodimentthereof, Figures 2 and 2A are a series of graphs illustrating the pulsesoccurring throughout the system, and Figure 3 is a wiring diagram of thevarious connections of Fig. 1. Similar reference numerals are applied tosimilar elements throughout the drawing.

Referring to Figure 1, a motor l having a shaft 2 synchronously drives aflat disc 3 in phase with a second fiat vdisc 4. One half ofthe fiatdisc 3 has an opaque portion 5 while the other half of the disc istransparent and has regularly spaced opaque ilducial marks 6 near itsperiphery and an interior transparent portion 1. One half of the secondflat disc 4 comprises an opaque section 8. The remaining half of thedisc 4 is transparent and has irregularly spaced opaque flducial marks 9near its periphery while the interior portion I 0 is transparent. Thespacing of the iiducial marks 9 is determined by the function of thevariable X which is to be generated.

A light source i I actuated by a source of power,

such as a battery I2, is focused upon the ducial marks 6 of the disc 3by means of a lens I3 and an apertured mask I4. The light, afterinterruption by the nducial marks 6, is focused upon a first lightsensitive device I bya second lens I6. Light from the source II is alsoapplied simultaneously to a second light sensitive device I1 through thetransparent inner portion of the rotating disc 3 during each alternatehalf revolution thereof.

Similarly, a. second light source 2I is energized by a second powersource, such as a battery 22. Light from the light source 2l is focusedupon the fiducial marks 9 of the second disc 4 by means of a third lens23 and a second apertured mask 24. The light, after interruption by thefiduoial marks 9, is focused upon a third light sensitive device 25 bymeans of a fourth lens 26. Light from the source 2I is also transmittedsimultaneously through the transparent inner portion of the second disc4 to a fourth light sensitive device 21 during alternate halfrevolutions of the second disc 4.

The value of the variable X may be represented by a series of regularlyoccurring voltage pulses which are applied to the input terminals 28,29, These regularly occurring pulses may be derived in any manner wellknown in the art.

A control voltage, derived from the second light sensitive device I1during the interval that the opaque portion 5 of the first disc 3obscures the rst light source II, operates a first electronic switch 30to apply the input X pulses to be counted upon a conventional electroniccounter 3I, which may be of the general type described in the copendingapplication referred to heretofore. The voltage generated by the secondlight sensitive device I1, during the interval when it is actuated bylight from the first light source II, next actuates the first electronicswitch 30 to discontinue the application of the X pulses to the Xcounter 3I and to apply voltage pulses derived from the firstlight-sensitive device I5 to subtract from the counter 3l. When thecounter is completely cleared, a control signal is derived therefrom andapplied to a control circuit 32 which actuates a second electronicswitch 33.

During the interval that the light from the second light source 2| isapplied to the fourth light sensitive device 21, a control potential isderived from the light sensitive device which opens the circuit througha third electronic switch 34. During this period, the pulses derivedfrom the third light sensitive device 25 are supplied through the switch33 and counted upon a second f (X) counter 35 for recording the functionof X. When the zero signal is applied by the X counter 3I to the controlcircuit 32 it operates the second electronic switch 33 to interrupt theapplication of the pulses from the third light sensitive device 25 tothe ,f(X) counter 35. It will be seen, therefore, that the f(X) counter35 records the pulses from the third light sensitive device 25 at thesaine time that the pulses from the first light sensitive device I5 arebeing subtracted from the X counter 3|. If desired, the count recordedupon the f(X) counter 35 may be indicated upon a plurality of gaseousdischarge lamps =44, 45, 46, 41, 48 in the manner described in thecopending U. S. application mentioned heretofore.

Similarly, while the two light sources II and 2I are obscured by theopaque portions 5 and 8 of the discs 3 and 4, respectively, the X pulsesare set up in the X counter 3I and the MX) nais 36, 31.

plished, for example, by a pulse oscillator 38,

count upon the second counter 35 is caused to be subtracted and appliedto the output termi- This subtraction may be accomand is controlled byoperation of the third electronic switch 34 in response to the absenceof a control voltage from the fourth light sensitive device 21 which isconnected Qiereto A counter adapted to both counting and subtraction isdescribed in the copending U. S. application mentioned heretofore.

Referring to Figure 2, which represents the condition for the maximumvalue of the function, it will lbe seen that the regularly occurring Xpulses A4I) occur during some portion of the first half of eachrevolution of the disc 3 while the opaque portion 5 of the disc obscuresthe second light-sensitive device II. These pulses are recorded upon theX counter 3l. During the next succeeding half revolution of the discs 3and 4, pulses 4I derived from the light-sensitive device I5 uncount theX counter, while pulses 42 derived from the third light-sensitive device25 are counted simultaneously upon the ;f(X) counter 35.

During the next repetition of the first half revolution of both discs, Xpulses 40 are again counted upon the X counter 3I, while the HX) pulses43 are subtracted from the f(X) counter 35 and applied to the outputterminals 36, 31.

Fig. 2A is a continuation of Fig. 2 and represents the condition for aless than maximum value of the function. This value is of courseselected in response to the value of X set up in the counter 3I duringthe last half revolution shown by Fig. 2.

It should be understood that the pulses may be counted and subtractedfrom the respective counters by the method disclosed in the copendingapplication mentioned heretofore, or in any other manner known in theart.

Since the timing of the two discs is mechanically synchronized by therotation of a common shaft, speed variations thereof may besubstantially disregarded, providing each count and uncount is completedin less time than is required for a half revolution of the shaft 2.

It should be understood further that variations of the mechanical,optical and electrical elements may be employed in any manner Well knownin the art. For example, rotating cylinders may be utilized instead ofrotating discs. Also, the ilducial marks may extend completely aroundthe discs or cylinders, and pulses may be derived therefrom on alternaterevolutions by any known switching means.

In considering the wiring diagram of Fig. 3, it is helpful to rememberthat the cycle of operation involves one period when light reaches thevarious photocells and another period when no light reaches these cells.During the dark period, (i) the cell I1 operates to connect the leads28-29 through the switch 30 to the set-up device 3l so that a value of Xis established or stored in this set-up device and (2) the photocell 21operates to maintain the switch 34 closed so that any number establishedin the set-up device 35 is transferred to the leads 36-3'I.

The cells I5 and 25 perform no useful function during this dark period.

During the light period which follows (l) the cell 21 operates to openthe switch 34, (2) the cell 25 operates to store a value of the functionf in the set-up device 35, (3) the cell I1 interrupts the connection tothe leads 2li- 29, and (4) the cell I5 operates through the switch 38 toturn back the device 3| till it registers zero. When the device 3|registers zero, a pulse from the device 3| functions to open the switch33. Otherwise stated, the value of the function is derived from the disc4 and stored in the set-up device 35 during one-half revolution of thediscs 3 and 4 and is delivered at the output terminals 36-31 during thenext one-half revolution of these discs. The selected value of thefunction is, of course, determined by the X value established in thedevice 3|.

The set-up devices 3| and 35 in which the X and f(X).values are storedare of a well known type which includes a plurality of multivibratorunits interconnected through transfer tubes. Thus the device 3| includesunits 50 to 53, the units 50 and 5| being connected through transfer orblocking tubes 54 and 55, the units 5| and 52 being connected throughtransfer tubes 56 and 51, and the units 52 and 53 being connectedthrough the transfer tubes 58 and 59.

The switch includes a pair of tubes 60 and 6| which have their gridpotentials controlled by the cell |1 to which a battery 62 is connectedthrough resistors 63 and 64. When the cell |1 is not illuminated, itconducts little or no current, the grid of the tube 6| is at a morepositive potential, and the grid of the tube 60 is at a more negativepotential. Under these conditions, the tube 6| conducts current, thetube 66 is biased down, a more positive potential is applied to thegrids of the tubes 55, 51 and 59 which are biased to cut off and a morenegative potential is applied to the grids of the tubes 54, 56 and 58which are biased beyond cut oil. Under these conditions, the device 3|stores the pulses applied to the leads 28-29 and through these leads anda control tube 65 to the common anode terminal of the unit 53. Each ofthese pulses (applied to the leads 28-29) increases the current of thetube 65 and causes a negative pulse to be applied to the common anodeterminal.

Thus, the nrst pulse transfers current from the left to the right-handside of the unit 53; the second pulse transfers current to the left sideof the unit 53 and produces at the grid of the tube 59 a positive pulsewhich increases the current of the tube 58 and produces at the commonanode terminal of the unit 52 a negative pulse by which current istransferred to the right-hand side of this unit; and the third pulsetransfers current to the right side of the unit 53. I'here are now threepulses stored in the device 3|. Further steps in the operation of thedevice 3| are apparent from the following tabulation, remembering thattubes 54, 56 and 58 are blocked and 55, 51 and 59 are biased for normaloperation. In this tabulation an R indicates that the right side of theunit is conducting and an L indicates that the left side of the unit isconducting.

Pulse No. Tnit N'fl'nit 5" 'init 5.' "'nit 53 tube 36 has for itspurpose to terminate the supply of pulses from the cell 25 to thecounter 35 when the count of the counter 3| is reduced to zero and thezero signal is applied to the switch 33.

When the cell I1 is illuminated and takes current, the tubes 55, 51 and59 are biased beyond cut on', the tubes 54, 56 and 56 are provided withtheir normal bias, and the device 3| is in a condition to have itsstored number diminished in response to pulses applied from the cell I5through the tube 65 to the common anode terminal of the unit 53. Turningback of the device 3| to zero may be done with any number of storedpulses. Assuming ve pulses to have been stored in the device 3|, thevarious steps are indicated by the following tabulation:

Pulse No. Unit 5G Unit 5' 'Init 52 Unit 53 5 L R L L l L L R R 2 L L R LL L L R L L L L R R R R It is apparent that the fth subtracting pulseresults in a, more negative potential at the grid of the tube 66 and theinterruption of the supply of pulses from the cell 25 through the tube66 to the device 35.

The device 35 is similar to the device 3| with the exception that itsstoring and subtracting operations are controlled by the cell 21 and theswitch 34 and its subtracting pulses are supplied from the generator 38.It includes units 61 to 10, the units 61 and 68 being interconnectedthrough the tubes blocking or transfer tubes 1| and 12, the units 68 and69 being connected by the tubes 13 and 14 and the units 69 and 10 beingconnected by the tubes 15 and 16.

The cell 21 is connected to a battery 8| through resistors 82 and 83 andfunctions to control the grid potential of tubes 84 and 85. With noillumination on the cell 21, the grid of the tube 64 is more positiveand that of the tube 85 more negative, the tubes 12, 14 and 16 arebiased beyond cut oiT and the tubes 1|, 13 and 15 are provided withnormal bias and the tube 66 transmits subtracting pulses from thegenerator 38 to the common anode terminal of the unit 10. These pulsessubtract from the count stored in the device 35 in the same manner asthat set forth in connection with the device 3| and the cell I5. Whenthe subtraction operation is complete, a pulse applied through the lead11' operates to interrupt the supply of oscillations from the generator38.

When the cell 21 is illuminated, the tubes 1 I, 13 and 15 are biasedbeyond cut on', the tube 66 is biased off and the tubes 12, 14 and 16are provided with normal bias. Under these conditions, pulses aresupplied from the cell 25 through the tube 66 to the device 35 aspreviously indicated.

Obviously, the devices 3| and 25 will include as many units as arerequired to express the desired function in the binary numerical systemas point'- ed out in the aforesaid application Serial No. 464,293.

Thu-s the invention described comprises an improved method of and meansfor generating voltage pulses which are a, predetermined function ofother applied pulses which represent the instantaneous value of avariable quantity.

I claim as my invention:

1. The combination of first and second set-up devices, means forestablishing in said first device a representation of the value of avariable, synchronously operated sources of timing pulses and offunction pulses timed with respect to said timing pulses in accordancewith a function of said variable, means for applying said timing pulsesto change said representation to represent progressively lower values,means for establishing in said second device a representation of saidfunction pulses simultaneously with said change in representation, andmeans for interrupting the supply of said function pulses to said seconddevice in response to a zero value representation of said first device.

2. The combination of first and second set-up devices, means forestablishing in said first device a representation of the value of avariable, synchronously operated sources of timing pulses and offunction pulses timed with respect to said timing pulses in accordancewith a function of said variable, means for applying said timing pulsesto change said representation to represent progressively lower values,means for establishing in said second device a representation of saidfunction pulses simultaneously with said change in representation, andmeans controlled by said second device for delivering a number of pulsesdetermined by the representation in said second device simultaneouslywith the establishment in said first device of a representation of asuccessive value of said variable.

3. The combination of rst and second set-up devices, means forestablishing in said first device a representation of the value of avariable, synchronously operated sources of timing pulses and offunction pulscs timed with respect to -said timing pulses in accordancewith a function of said variable, means forl applying said timing pulsesto change said representation to represent progressively lower values,means for establishing in said second device a representation of saidfunction pulses simultaneously with said change in representation, andmeans including a continuously operating generator controlled by saidsecond device for delivering pulses determined by the representationestablished therein.

4. The combination of first and second set-up devices, means forestablishing in said first device a representation of a value of avariable, a first merrber having a timing record, a second member havinga function record, means for simultaneously moving said members, meansresponsive to said timing record for changing said representation torepresent progressively lower values. means responsive to said functionrecord for estab'ishing in said second device a representation of thevalue of a function of said variable, and means responsive to a zerovalue representation of said first device for terminating theestablishing of said function value representation.

5. The combination of first and second set-up devices, means forestablishing in said first device a representation of a value of avariable, a first member having a timing record, a second member havinga function record, means for simultaneously moving said members, meansresponsive to said timing record for changing said representation torepresent progressively lower values, means responsive to said functionrecord for establishing in said second device a representation of thevalue of a function of said variable, an output circuit and meanscontrolled by said second device for delivering from said output 8terminals pulses determined by said function value representation.

6. The combination of first and second set-up devices, means forestablishing in said rst device a representation of a value of avariable, a first member having a timing record, a second member havinga function record, means for simultaneously moving said members, meansresponsive to said timing record for changing said representation torepresent progressively lower values, means responsive to said functionrecord for establishing in said second device a representation of thevalue of a function of said variable, and means including a continuouslyoperating generator controlled by Isaid second device for delivering anumber of pulses determined by said function value representation.

'1. The combination of first and second set-up devices, means forestablishing in said first device a representation of a value of avariable, a first member having a timing record, a second member havinga function record, means for simultaneously moving said members, meansresponsive to said timing record for changing said representation torepresent progressively lower values, means responsive to said functionrecord for establishing in said second device a representation of thevalue of a function of said variable, means including a pulse generatorfor changing the representation established in said second device, andmeans responsive to a zero value representation of said second devicefor terminating the effect of said generator on said second device. 4

8. The combination of first and second set-up devices, means forestablishing in said first device a representation of one value of avariable, a first member provided with opaque, transparent and timingrecord areas, a second member provided with opaque, transparent andfunction record areas, means for simultaneously moving said members,means responsive to light transmitted through the transparent, area ofsaid first member for terminating said representation, means forderiving from said timing record timing pulses whereby saidrepresentation is changed to represent progressively lower values, meansresponsive to said function record for establishing in said seconddevice a representation of the value of a function of said variable, andmeans responsive to a zero value representation of said first device forinterrupting the establishing of said function value representation insaid second device.

9. The combination of first and second set-up devices, means forestablishing in said first device a representation of one value of avariable, a rst member provided with opaque, transparent and timingrecord areas, a second member provided with opaque, transparent andfunction record areas, means for simultaneously moving said members,means responsive to light transmitted through the transparent area ofsaid first member for terminating said representation, means forderiving from said timing record timing pulses whereby saidrepresentation is changed to represent progressively lower values, meansresponsive to said function record for establishing in said seconddevice a representation of the value of a function of said variable,output terminals, and means responsive to said second member forcontrolling the delivery to said output terminals of a number of pulsesdetermined by said function value representation.

JAN A. RAJCHMAN.

